In recent years, as portable electronic devices (e.g., mobile phones and digital cameras) become ubiquitous, much effort has been put into reducing dimensions of portable electronic devices. Moreover, as dimensions of charged coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) based optical sensors are reduced, dimensions of imaging lenses for use with the optical sensors must be correspondingly reduced without significantly compromising optical performance. However, the most important characteristics of imaging lenses are imaging quality and size.
In view of the increasing demand for imaging quality, the structure of the traditional four-piece lens may no longer be able to meet the higher demand. Therefore, it is required to develop a more high-end imaging lens, for example, an imaging lens of six-piece lens, to achieve better imaging quality.
Each of U.S. Pat. Nos. 7,663,814 and 8,040,618 discloses a relatively long conventional imaging lens that includes six lens elements. Each of these conventional imaging lenses has a system length of over 21 mm, which disfavors reducing a thickness of portable electronic devices, such as mobile phones and digital cameras.
Therefore, producing an imaging lens that meets requirements of consumer electronic products while having satisfactory optical performance is always a goal in the industry.